In spite of many advances over the last 30 years cancer remains a major cause of mortality. It is estimated that globally cancer is responsible for 13% of all deaths, approximately 7.6 million. In the western world incidence is increasing due to increased lifespan and changes in lifestyle. It is clear that novel forms of therapy are required especially for the most common cancers such as lung, colorectal and liver cancers. Advances have been made in the treatment of early stage breast and prostate cancer but when they recur these diseases are highly refractory to treatment.

Our group focuses on the identification and validation of novel targets for cancer therapy and on the discovery of novel small molecule compounds that could be developed into therapeutic agents. We specialize in the use of advanced automated methods that include the High Throughput Screening, (HTS) of small molecule and natural product libraries and High Content Screening which involves the use of automated microscopy and subsequent automated image analysis to extract multiparameter data from cell-based assays.

Our group also runs the Cell Screening Center and so has access to the Center's automated cell screening platform and libraries for our work. We currently have two projects in progress:

Chemical biology of lysosomal cell death

The primary goal of this project is to identify novel anti-cancer compounds that kill via the caspase-independent lysosomal cell death (LCD) pathway. Secondary goals include a greater understanding of the chemical biology of so-called "alternative cell death pathways" and the developemnt of novel technologies for cancer drug discovery.

Apoptosis (programmed cell death), represents a universal, caspase-dependent cell death pathway and is the target of many currently used tumor therapies. However, tumor cells often undergo genetic changes that make them resistant to apoptotic cell death.

Cathepsins are a family of lysosome-bound proteases that are optimally active at the acidic pH of the lysosome and partially active at neutral pH outside the lysosome. In circumstances of lysosomal membrane permeabilization (LMP) cathepsins leak through the lysosomal membrane into the cytoplasm, where they can induce programmed cell death. LMP is triggered by a variety of agents including reactive oxygen species and small molecules. Depending on the cellular context, LMP leads to caspase-depedent apoptosis or caspase-independent, apoptosis-like cell death. The latter pathway is referred to as the lysosomal cell death (LCD) pathway, (Figure 1). This pathway is of great potential therapeutic interest since many tumor cells acquire resistance against caspase-dependent apoptosis inducers.

cell death pathways

Figure 1. The apoptotic and lysosomal cell death pathways.

The LCD pathway is of interest as a target in those tumors that are resistant to apoptosis. Moreover, upon transformation, tumor cells - especially breast cancer cells - show many changes in their lysosomal system, which selectively increases their vulnerability to LCD. For these reasons small molecules that target the LCD pathways may be useful as cancer therapeutics. In this project we are running high throughput screens to identify small molecules that kill cancer cells via LCD. The project utilizes multi-disciplinary expertise in high throughput screening, cell biology, medicinal chemistry, high content analysis and bioinformatics, and yeast gene expression profiling.

  • Project Leader: Dr. Romina J. Pagliero
  • Technician: Daphne Lelieveld
  • Collaborators: Prof. Judith Klumperman, Prof. Marja Jaatella, Prof. Rob Liskamp, Prof. Jeroen den Hertog

Small molecule disruptors of the growth hormone receptor-JAK2 interaction

Recent studies in animals show that growth hormone (GH) is required for the induction of breast and other tumors. They also show that GH injected in GH-knock-out mice increases tumor-incidence, and that cessation of the GH replacement results in disappearance of the tumors. In addition, estrogen-independent tumors are reduced in size and number, if tumor-prone mice are crossed with GH receptor (GHR) knock-out animals. Many other studies show clear evidence for the occurrence of malignancies related to body length and growth rate in puberty.

Previous work from Prof. Ger Strous has revealed that the GHR activity is controlled by two factors. Both bind to highly specific motifs of the GHR: the ubiquitin ligase, TrCP2, induces GHR degradation while the kinase, Jak2, stabilizes the receptor at the cell surface. If no Jak2 is present, the GHR is immediately degraded via TrCP2 action. Although TrCP2 and Jak2 are involved in many signaling processes in the cell, their interactions with the GHR are unique.

Based on this knowledge we have established a project to validate the GHR-JAK2 interaction as a novel target for the treatment of breast cancer. We will use an in vitro assay to identify small molecules compounds that interfere with the binding of Jak2 to the dimerised cytosolic tails of the GHR. The assay is state-of-the-art as it is optimized for the spatial proper orientation of Jak2 towards the different domains of the GHR. Active compounds will be tested in cell culture for their effects on GHR degradation and signal transduction. Active compounds will be optimized for efficacy by medicinal chemistry and these compounds will be tested in tumor-induced and bearing mice for their anti-cancer effects.

  • Project Leader: Dr. Lieke van der Velden
  • Technician: Elisabeth van der Vaart
  • Collaborators: Prof. Judith Klumperman, Prof. Ger Strous, Prof. Rob Liskamp, Prof. Jeroen den Hertog